1. Field of the Invention
This invention relates to circulating valves used in testing and pumping operations in a wellbore, and more particularly, to a circulating valve with a standing valve for preventing fluid loss to a well formation when a packer is set therebelow with the circulating valve in the open position.
2. Description of the Prior Art
The Halliburton retrievable test-treat-squeeze (RTTS) packer system includes a multi-purpose hook wall-type retrievable packer designed for use in testing, treating and squeezing operations in a wellbore. The system also includes a two-position circulating valve.
The packer is set by apploying right-hand torque to the tool string and setting down weight. This action causes mechanical slips in the packer to engage the wall of the casing. These slips then support the tubing weight required to compress rubber packer elements to cause them to seal against the casing. The mechanical slips also support any hydraulic load in the well annulus above the packer, such as when the tubing is swabbed.
A hydraulic hold-down with large slips is built into the packer above the packer elements. These hydraulic slips engage the casing only when pressure is applied through the tubing to the area below the packer to resist any upward movement of the packer due to the force created by the pressure thereunder.
During pumping and testing operations of the tool, the circulating valve is locked closed. When desired, it may be opened to allow circulating above the packer and later reclosed.
Both the packer and circulating valve have large bores therethrough which permit the pumping of large volumes of liquid with a minimum pressure drop. A problem may arise when it is not desirable to place a large volume of fluid on the well formation prematurely. Some formations cannot handle the weight of the fluid, and the fluid may be lost by dissipation through the formation.
The circulating valve of the present invention solves this problem by modifying the prior art valve to provide a removable standing valve therein. The standing valve is similar to that used in the Halliburton Pin Point Injection (PPI) Packer. The standing valve keeps hydrostatic head off the formation before fracturing treatment to prevent fluid loss to the formation.
The circulating valve also acts as a positive circulating valve with a forced flow path through which chemicals, such as acid, may be spotted. For example, a very small amount of acid may be spotted through the tubing to clean out scale.
After this operation, the standing valve may be removed by a retrievable tool on a wireline, and subsequently, the circulating valve may be operated at high flow rates to conduct normal fracturing/treating jobs in the same manner as the prior art RTTS circulating valve.
After the treatment has been performed, the standing valve may be returned to its position in the circulating valve. The circulating valve may then be opened, and the annular fluid above the packer may be recovered without losing it to the formation.